I wanted to monitor outgoing messages for the IoT Hub built-in Event Hub but I seem there is no possibility to access this metric.
There are some metrics which give some insight. For example "Routing: messages delivered to messages/events" (namespace: microsoft.devices/iothubs, metricID: d2c.endpoints.egress.builtIn.events) which shows number of messages send to built-in Event Hub. But I cannot see outgoing messages for this built-in Event Hub.
If I use Event Hubs directly I can monitor this metric (namespace: microsoft.eventhub/namespaces, metricID: OutgoingMessages) plus Event Hub specific metrics.
How can I monitor outgoing messages for the IoT Hub built-in Event Hub (without first forwarding to an Event Hub)?

